Linear guide bearing apparatus

ABSTRACT

In a linear guide bearing apparatus wherein a separator is interposed between adjacent balls K and K moving following a curved circulating path  8 , and the ball K contacts concave faces W of the separator T at both ends in an axial line direction and at the same time the ball K rolls as contacting a guide face  8   a  of an outside guiding member  5  and a guide face  8   b  of an inside guiding member  9 , the separator has an outer diameter larger than a maximum outer diameter Lφ under a condition where the ball rolls as simultaneously contacting both curved faces  8   a   , 8   b  of the inside and the outside of the curved circulating path  8 , and the radius of curvature of the guiding face  8   b  in the curved circulating path  8  is reduced to a size not contacting the separator T.

This is a divisional of application Ser. No. 09/756,182 filed Jan. 9,2001, now U.S. Pat. No. 6,663,285; the disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a linear guide bearing apparatus making use ofrolling of balls, and in particular to an improvement of a linear guidebearing apparatus interposing separators between the balls.

2. Description of the Related Art

As a linear guide bearing apparatus of the related art making use ofrolling of balls, for example, there is, as shown in FIG. 7, a linearguide apparatus which is furnished with a guide rail 1 elongated in anaxial direction and a slider 2 movably crossing thereover. The guiderail 1 is defined at both sides with ball rolling grooves 3 respectivelyin the axial direction. On the other hand, as shown in FIG. 8 being across sectional view, a main body 2A of a slider 2 is defined with ballrolling grooves 6 in opposition to the ball rolling grooves 3 at theinside of both wings 4.

Both opposite ball rolling grooves 3, 6 form a loading ball rolling pathA, and balls K of many steel balls roll while supporting load, so thatthe slider 2 move on the guide rail 1 in the axial direction. Followingthis moving, the ball K intervened between the guide rail 1 and theslider 2 moves to an end part of the main body 2A of the slider 2, andin order to continuously move the slider in the axial direction, theballs K must be unlimitedly circulated.

Therefore, a linear penetrating hole 7 is formed as a ball returningpath axially penetrating in the wings 4 of the slider main body 2A, andat the same time, end caps 5 are equipped at both front and rear ends ofthe slider main body 2A, where a ball circulating path 8 is formed whichis curved in half toroid for communicating the loading ball rolling pathA of both ball rolling grooves 3 and 6 with the ball returning path 7,thereby to compose an endless ball circulating path. The ballcirculating path 8 is composed of an outside guiding face 8 a and aninside guiding face 8 b. The outside guiding face 8 a is a semi arcgroove formed in the inside end of the end cap 5 being an outsideguiding member. The inside guiding face 8 b is an outer circumference ofa half column shaped inside guiding member 9 (also called as returnguide) secured to the end face of the slider main body 2A.

Although not shown in FIG. 8, there is also a case that the separator T(also called as retaining piece), as shown in FIG. 9, interposed betweenthe adjacent balls K and K in the unlimited circulating path.

Applicant invented linear guide apparatus of improving operatingperformance by specifying sizes and shapes of the separator T (JapanesePatent Application No. Hei.11-166900). This is, as shown in FIG. 9, thatthe separator T is substantially cylindrical at an outer circumference Qand has concave parts W at both sides for contacting the balls K. Undera condition that the balls K are contacted with the concave faces W, anaxial line L of the separator coincide with a straight line combiningcentral points O and O of the adjacent balls K and K, and the radius ofcurvature of the concave face part W contacting with the ball K isalmost equal to the radius of the ball K.

The separator T has effects of suppressing zigzag phenomena of the ballto heighten the operating performance and suppressing noises to heightennoise characteristics. The larger the holding margin of the ball, thatis, the larger the outer diameter Lφ of the separator T, the larger theeffects, and a maximum outer diameter size is regulated to be sizesinterfering with the inside guiding member 9. FIG. 9 shows a conditionwhere the ball K rolls while contacting with both of the outside guidingface 8 a and the inside guiding face 8 b of the ball circulating path 8,namely, a condition of “no space and no playing”. The maximum value Lφof the outside dimension of the separator T can be expressed thefollowing formula (1) based on a theorem of three dimensional square.Lφ=2{(L _(R) −Da/2)²−(L _(SP)/2)²}^(1/2)−2L _(r)  (1)herein,

-   -   Lφ: the maximum outer diameter when the separator T makes no        playing

Da: the ball diameter

L_(SP): span between balls

L_(R): the radius of the outside guiding face 8 a

L_(r): the radius of the inside guiding face 8 b.

Under the condition of “no space and no playing” of the balls K withrespect to the inner and outer guiding faces 8 a, 8 b of the ballcirculating path 8, since the balls do not always roll smoothly, takingthe allowable dimensional precision in production into consideration, itis general to prepare playing of about 10% of the ball diameter betweenthe ball K and the ball rolling circulating path 8, irrespective ofpresence or absence of the separator T.

FIG. 10 shows a case of a general ball circulating path 8 providingsomewhat playing in rolling of the ball K, and the maximum outerdiameter size Lφ_(max) of the separator T at this time is expressed bythe following formula (2), which can be made larger than the maximumouter diameter Lφ without preparing the playing.Lφ_(max)=2{(L _(R) −Da/2)²−(L _(SP)/2)²}^(1/2)−2(L _(R) −Da−Ld)  (2)herein,

-   -   Lφ_(max): the maximum outer diameter of the separator T (a        little playing)    -   Lφ: the maximum outer diameter when the separator T makes no        playing

Da: the ball diameter

-   -   L_(SP): span between balls    -   L_(R): the radius of the outside guiding face 8 a    -   L_(r): the radius of the inside guiding face 8 b    -   L_(d): the amount of “playing”

However, the separator T having the maximum outer diameter size Lφ_(max)under the condition of “with playing” (FIG. 10) of the linear guidebearing apparatus shown in JP-A-11-166900 is involved with the problemthat the outer diameter of the separator T is made as large as possiblefor heightening the ball holding effect by enlarging a holding margin,but the interference with the slider main body 2A is created so that itis difficult to provide an improving effect of sufficient operatingperformance. In short, as shown in FIG. 10, it is preferable that alittle playing is present between the ball K and the inside guidingmember 9 in the ball circulating path 8, but in contrast, the ball Kmust not have the playing in the loading ball rolling path A. Thus, acorner portion C which is present at an edge in the loading ball rollingpath A of the slider main body 2A equipped with the inside guidingmember 9 (return guide) in the ball circulating path 8, cannot butinevitably be a little protruded toward the loading ball rolling path A.This protruded corner portion C interferes with the separator T.

The above mentioned patent application showes that it is effective toregulate the maximum outer diameter Lφ_(max) of the separator T withinthe range of 60 to 80% of the ball diameter Da. But, when using theseparator T as large as possible which is an outer diameter of about 70to 80% near to the upper limit, in order to avoid the interference, theinside guiding face 8 b of the inside guiding member 9 is made acomposite curve comprising a plurality of curves different in centersand radii of curvature, not a simple semicircle, so that the insideguiding member 9 is remarkably complicated in shape, inviting cost-up.

Inventors noticed unsolved problems of the related art, made studies andfound that even if the playing becomes larger to a certain degreebetween the ball and the inside guiding member in the ball circulatingpath, an effect for heightening the ball holding function by enlargingthe outer diameter of the separator T exceeds an influence by theplaying, and as a result, the operating performance of the linearguiding apparatus

is improved, and have realized this invention.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide a moreeconomical linear guide bearing apparatus where, using a separator T ofan outer diameter as large as possible, the separator can be preventedfrom interference with a ball circulating path or a slider main body,enabling to heighten operating performance, noise characteristics anddurability.

For accomplishing the above mentioned object, a first aspect of theinvention is a linear guide bearing apparatus, wherein guiding ballshave parts which move following a curved circulating path regulated byguiding members, a substantially column or cylindrical separator isinterposed between adjacent balls in such a manner that a straight linecombining center points of the adjacent balls is parallel to coincidesto an axial line of the separator, and concave faces in both ends of theseparator in the axial direction respectively contact spherical surfacesof the adjacent balls, characterized in that the separatorsimultaneously contacts both curved faces of an inside and outside inthe curved circulating path while the separator has a size of an outerdiameter more than a maximum size of an outer diameter under a conditionwhere the ball rolls, a radius of curvature of an inside curve in thecurved circulating path is reduced to a size not contacting theseparator, and a radius of curvature of an outside curve in the curvedcirculating path is enlarged to a size not contacting the inside curveand the separator.

A second aspect of the invention is a linear guide bearing apparatus,wherein guiding balls have parts which move following a curvedcirculating path regulated by guiding members, a separator is interposedbetween adjacent balls in such a manner that a straight line combiningcenter points of the adjacent balls coincides to an axial line of theseparator, and concave faces in both ends of the separator in the axialdirection respectively contact spherical surfaces of the adjacent balls,characterized in that the separator simultaneously contacts both curvedfaces of an inside and outside of the curved circulating path while theseparator has a size of an outer diameter more than a maximum size of anouter diameter under a condition where the ball rolls, and a chamferingfor preventing interference with the separator is processed at a cornerportion of an edge in the ball rolling circulating path of a main bodyof the linear guide bearing apparatus furnished with an inside memberforming an inside curve in the curve circulating path.

A third aspect of the invention is a linear guide bearing apparatus,wherein guiding balls have parts which move following a curvedcirculating path regulated by guiding members, a separator is interposedbetween adjacent balls in such a manner that a straight line combiningcenter points of the adjacent balls coincides to an axial line of theseparator, and concave faces in both ends of the separator in the axialdirection respectively contact spherical surfaces of the adjacent balls,characterized in that the separator simultaneously contacts both curvedfaces of an inside and outside in the curved circulating path while theseparator has a size of an outer diameter more than a maximum size of anouter diameter under a condition where the ball rolls, and has an outerdiameter of less than 95% of the ball diameter.

A fourth aspect of the invention is a linear guide bearing apparatus,wherein guiding balls have parts which move following a curvedcirculating path regulated by guiding members, a separator is interposedbetween adjacent balls in such a manner that a straight line combiningcenter points of the adjacent balls coincides to an axial line of theseparator, and concave faces in both ends of the separator in the axialdirection respectively contact spherical surfaces of the adjacent balls,characterized in that the separator simultaneously contacts both curvedfaces of an inside and outside of the curved circulating path while theseparator has a size of an outer diameter more than a maximum size of anouter diameter under a condition where the ball rolls, and concave partsare provided at outer circumferences of the outer diameter of theseparator for preventing interference with the inside curve in the curvecirculating path.

A fifth aspect of the invention is a linear guide bearing apparatus,wherein guiding balls have parts which move following a curvedcirculating path regulated by guiding members, a separator is interposedbetween adjacent balls in such a manner that a straight line combiningcenter points of the adjacent balls coincides to an axial line of theseparator, and concave faces in both ends of the separator in the axialdirection respectively contact spherical surfaces of the adjacent balls,characterized in that the separator simultaneously contacts both curvedfaces of an inside and outside in the curved circulating path while theseparator has a size of an outer diameter more than a maximum size of anouter diameter under a condition where the ball rolls, and the outerdiameter face of the separator and the inside curve in the curvedcirculating path slidingly contact.

A sixth aspect of the invention is a linear guide bearing apparatus,wherein guiding balls have parts which move following a curvedcirculating path regulated by guiding members, a separator is interposedbetween adjacent balls in such a manner that a straight line combiningcenter points of the adjacent balls coincides to an axial line of theseparator, and concave faces in both ends of the separator in the axialdirection respectively contact spherical surfaces of the adjacent balls,characterized in that the separator simultaneously contacts both curvedfaces of an inside and outside of the curved circulating path while theseparator has a size of an outer diameter more than a maximum size of anouter diameter under a condition where the ball rolls, and the separatoris provided with a projection on the outer diameter face, and theprojection and the inside curve in the curved circulating path slidinglycontact.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are cross sectional views of curved raceway partsshowing a first embodiment of the linear guide bearing apparatus of theinvention;

FIGS. 2A to 2E are explanatory views of variations in frictional forcefor evaluating the operating performance of the separator per each ofthe outside dimensions with respect to the ball diameter;

FIG. 3 is an explanatory view of evaluating the outside dimensions ofthe separators with respect to the ball diameter;

FIG. 4 is a cross sectional view of the curved raceway part showing thesecond embodiment of the linear guiding apparatus of the invention;

FIG. 5 is a cross sectional view of the curved raceway part showing thethird embodiment of the linear guiding apparatus of the invention;

FIG. 6 is a cross sectional view of the curved raceway part showing thefourth embodiment of the linear guiding apparatus of the invention;

FIG. 7 is a perspective view of an outer appearance showing oneembodiment of the linear guide bearing apparatus of the related art;

FIG. 8 is a cross sectional view in the axial direction including thecurved raceway part of the linear guide bearing apparatus of FIG. 7;

FIG. 9 is a cross sectional view of the curved raceway part showing themaximum outer diameter of the separator under the condition of “no spaceand no playing”; and

FIG. 10 is a cross sectional view of the curved raceway part showing themaximum outer diameter of the separator with spaces.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Explanation will be made to the invention by way of the drawings. Thesame reference numeral and signs will be given to corresponding parts tothose of the related art for preventing repetition of explanation.

FIG. 1 shows a first embodiment of the linear guide bearing apparatus ofthe invention, and is a cross sectional view of a part of a curved ballcirculating path 8 composed of an outside guiding member 5 called as anend cap and an inside guiding member 9 called as a return guide.

In this embodiment, separators T having a solid cylinder shape areinterposed between adjacent balls K in such a manner that an axial lineL of the separator T coincides to a straight line combining centerpoints O of the adjacent balls K. The separator T has concave faces W inboth ends in the axial direction, radius of curvature of which issubstantially the same radius of curvature of the ball K. But, it issufficient that the concave face of the separator T contacts with thespherical face of the ball K at least in a vicinity of an outercircumferential parts thereof. A main body of the separator T is notnecessarily shaped in solid cylinder (column), but may be a hollowcylinder or spherical. What is requisite is that the separator T is easyto catch the ball K and a holding margin may be enlarged. From the aboveviewpoint, it is more advantageous that the separator T is shaped insolid cylinder than in sphere in the outer circumference, and that theseparator has a shape where the concave face and the ball K contact atmore outer circumferential parts of the concave faces W at both ends.

In the ball circulating path 8 where the ball K rotates under no load,as mentioned above, generally the ball is provided with a certainclearance for smooth circulation of the ball and allowable dimensionalprecision, but a play is caused thereby in the ball rolling to spoil theoperating performance and noise characteristics. With respect to minuseffects that the ball playing becomes large in the ball circulatingpath, the invention compensates it by increasing the outer diameter ofthe separator T so that a larger effect is brought about, thereby toheighten a ball holding function, consequently to improve the operatingperformance of the linear guide apparatus.

As one of means for increasing the outer diameter of the separator T aslarge as possible without interfering with the return guide 9 being theinside guide member, the present embodiment reduces the radius ofcurvature Lrd of the return guide 9 than the radius of curvature Lr incase of no playing (shown with a dotted line in FIG. 1). The outerdiameter Lφd of the separator T can be made thereby larger than theouter diameter Lφ at the time of no playing shown with a broken line andcan be expanded until a maximum outer diameter Lφd_(max). By increasingthe outer diameter of the separator T, it is possible to bring about aplus effect exceeding the minus effect of increasing the playing amountLdd caused by decreasing the radius of curvature of the return guide 9.

Although the interference with the separator T can be avoided byreducing the radius Lr of curvature of the return guide 9, depending onsizes in a space between the outer diameter Lφd of the separator T andthe radius Lrd of curvature of the return guide 9, the separator Tinterferes with a corner portion C at the edge of a slider main body 2Afurnished with the return guide 9 as shown in FIG. 1B and protrudingtoward A side of the rolling path of the loading ball. For stopping thisinterference, it is sufficient to chamfer the corner portion C at theend of the slider main body 2A. Thus, it is possible to circulate astill larger separator T by use of a return guide of simple shape asarc, thereby enabling to heighten the functioning performance at lowercost.

The relation between the playing amount Ldd and the outer diameter Lφdof the separator T is expressed by the following formula (3)Ldd=[(L _(SP)/2)²+{(Lφd/2)+Lrd} ²]^(1/2) −L _(r) d−Da/2  (3)herein,

-   -   Ldd: the playing amount    -   Lφd: the outer diameter of the separator    -   Da: the ball diameter    -   L_(SP): span between the ball    -   L_(r)d: the radius of the reduced inside guiding face 8 b

It is seen from this formula that the larger the outer diameter Lφd ofthe separator T, the larger the playing amount Ldd. From the results ofthe actual measurements, it was found that the ball holding effect bythe separator T surpassed the minus effect by the playing until aplaying amount of a certain degree, and an improvement of the operatingperformance was recognized, but if the playing amount was too much, azigzag phenomenon of the ball could not be controlled, and consequentlythe improvement of the operating performance was not acknowledged.

The allowable maximum outer diameter Lφd_(max) of the separator T isregulated by interference with the particular inside guiding member 9(return guide) among the guiding members. That is, since the separator Tis determined such that the axial line of the separator T coincides withthe straight line L combining the central points O of the adjacent ballsK, if the outer diameter size Lφd of the separator T is made large, theouter circumferential part comes nearer to the inside guiding member 9,and if making too large, both interfere each other. When the separator Tinterferes with the inside guiding member 9, the interference causes tomake noises, lower the operating performance or endurance. Accordingly,the maximum allowable value Lφd_(max) of the outside dimension of theseparator T is a value of contacting the inside guiding member 9.

Then, in response to the radius of curvature of the inside guiding face8 b of the return guide 9, separators T of various outer diameters wereused, and when ratios between the outside dimensions of those separatorsT and the diameters of the balls were 0.65 (65%), 0.80 (80%), 0.85 (85%)and 0.95 (95%), variations of dynamic friction of the separators Tmoving together with rolling of the balls in the ball circulating path 8were measured for evaluating the operating performance by the outsidedimensions Lφd of the separators T. The measured results are shown inFIGS. 2 and 3. The dynamic friction of the standard linear guide bearingapparatus without furnishing the separator T is shown in FIG. 2E. Ineach of the shown graphs, the axis of abscissa is the moving distance(mm) of the separator T, and the axis of ordinate is the dynamicfrictional force (kgf). Among variations in frictional force showntherein, taking sharp variations of the separators as shown in FIG. 2Einto consideration, sizes of maximum variation components per each ofthe separators are compared in FIG. 3. Since the size of the maximumvariation component of the standard without the separator is around 0.5kgf (shown with the dotted line in FIG. 3), if a condition when usingthe separator is 0.5 kgf or lower, the outside dimension Lφd of theseparator T is preferably less than 0.95 (95%).

As mentioned above, the linear guide bearing apparatus of the firstembodiment employs the separator T having the outer diameter Lφd whichis more than Lφ being the outer diameter of the separator T under thecondition where the ball K rolls while simultaneously contacting withboth inside and outside curved faces 8 a, 8 b in the ball circulatingpath 8, that is, under the condition which is designed such that theplaying of the ball K is zero in the ball circulating path 8 (or ifneeded, chamfering the end face of the slider main body continuing tothe inside curve 8 b of the ball circulating path 8), and the instantlinear guide bearing apparatus is composed in such a size that theradius of curvature of the inside curve 8 b in the ball circulating path8 is reduced to a size not contacting the separator T, otherwise, insuch a size that the radius of curvature of the outside curve 8 a in thecurved circulating path is expanded so that the inside curve and theseparator do not contact. Thereby, the interference between the ballcirculating path 8 and the separator T is prevented, and in comparisonwith the linear guide bearing apparatus having the return guide of thestandard size, the instant embodiment obtains an effect of moreimproving the operating performance and noise characteristics.

FIG. 4 shows a second embodiment of the linear guide bearing apparatusaccording to the invention.

This embodiment is different from the first embodiment in that a concave11 is defined in an outer circumferential part Q of the separator T,following the inside guide face 8 bof the ball circulating path 8.Therefore, in spite of the outer diameter of the same size as theseparator T of the first embodiment, that is, the area of a concavecontacting with the ball being the same size as in the first embodimentwhere the outer circumference Q is simple as a cylindrical face, theplaying amount Ld can be made smaller, to thereby bring about anadvantage of accomplishing lower noises.

FIG. 5 shows a third embodiment of the linear guide bearing apparatusaccording to the invention.

According to this embodiment, the outer circumference Q of the separatorT is slidably contacted with the inside guiding face 8 b in the ballcirculating path 8. This embodiment aims at more heightening theoperating performance and noise characteristics by suppressing thezigzag phenomena of the ball K to the most.

FIG. 6 shows a fourth embodiment of the linear guide bearing apparatusaccording to the invention.

This embodiment is different from each of the above mentionedembodiments in that a small projection 12 is provided on the outercircumference Q of the separator T, and via this small projection 12,the separator T contacts with the inside guiding face 8 b of the ballcirculating path 8. The contacting area between the separator T and theinside guiding face 8 b is made small so as to reduce the frictionalforce to the most for further heightening the operating performance andnoise characteristics.

Herein, a description will be given of the thickness of the separator Tregulating the span between the balls K and K. From the viewpoint ofload capacity of the linear guide bearing apparatus, the smaller thethickness of the separator T, the more preferable, but taking elasticdeformation or formability of the separator T into consideration, it isreasonable that the thickness of the separator is determined to bearound 3 to 10% of the ball diameter. In particular, when the ball isacted with large load, or loaded with large pre-load, the thickness ofthe separator T should be set as large as possible for increasingstrength. But the ball span L_(SP) is lengthened whereby and the outerdiameter Lφd_(max) of the separator is made small so that the ballholding forth of the separator T is lowered, and bad influences areprobably affected to the operating performance and noise characteristic.Even in such cases, if applying the invention, the ball holding force ofthe separator may be increased and it is possible to prevent badinfluences to the operating performance and noise characteristic.

In the above mentioned each of embodiments, an explanation has been madeto not only the shape of the inside guiding face 8 b but also the halftoroidal shape where the entire shape of the ball circulating path 8 issingle arc, but the ball circulating path 8 applied with the inventionis not limited to such shapes. For example, a shape combined with anelliptic shape and plural arcs, or coupled with an arc shape and astraight shape may be enough for the ball circulating path 8.

Shown is that the outer diameter of the separator T is shapedsubstantially in a solid cylinder, and a hollow cylindrical shape havinga penetrating hole at the center may be useful.

Explanation has been made to only independent separators T, butrespective separators may be connected.

The cases where the linear guide bearing apparatus is applied to thelinear guide apparatus are shown, but the invention may be suitablyemployed to other linear guide bearing apparatus such as linear ballbearings having the curved circulating paths.

As mentioned above, according to the invention, the outer diameter ofthe separator is made as large as possible, and concurrently theinterference between the curved circulating path and the separator islimited to the minimum, thereby to assume the effects of enabling tomore improve the operating performance and noise characteristics thanthe linear guide bearing apparatus of the standard specification withoutfurnishing the separator.

1. A linear guide bearing apparatus, comprising: a guide member having acurved circulating path defined by inside and outside curved faces; aplurality of balls moving along the curved circulating path of the guidemember; and a separator interposed between adjacent balls such that anaxial line of the separator is parallel to or coincides to a straightline combining center points of adjacent balls, the separator definingconcave faces at both ends thereof in the axial direction respectivelyat least partially contacting spherical surfaces of adjacent balls,wherein an outer diameter of the separator is such that an end of theseparator closer to the inner curved face extends towards the innercurved face farther from the outer curved face than a point on theradial line of the separator, said radial line being perpendicular tothe axial line and passing through a center of the separator, said pointbeing at a distance from the outer curved face equal to a diameter ofthe balls, and wherein an outer circumference of the outer diametersurface of the separator have a concave part for preventing interferencewith the inside curve in the curved circulating path.